The present invention relates to a W-CDMA transmission rate estimation method and device and, more particularly, to a W-CDMA transmission rate estimation method and device for estimating a transmission rate by using path metrics obtained in a Viterbi decoding process.
Schemes for IMT2000 W-CDMA system have been studied in 3GPP. A W-CDMA requires several parameters for implementing general functions in transmission processing and reception processing in FIGS. 1 and 2 to be described later. In W-CDMA or the like in which data with different transmission rates are integrated and transmitted, a parameter called a bit length is especially important for almost all functions.
As the function of notifying the receiving side of this bit length, a technique of sending information data called a TFCI (Transport Format Combination Indicator) has been studied (e.g., reference 1: Multiplexing and Channel Coding, 3G TS25.212 V3.1.1/1999-12).
Since the bit length parameter can change every 10 ms, the receiving side needs to know this parameter every 10 ms. The receiving side must therefore receive a TFCI every 10 ms. To eliminate the inconvenience of handling such a TFCI and effectively use channel capacity, a transmission rate estimation method (Blind Rate Detection) of estimating a bit length parameter on the receiving side without sending this TFCI has been proposed and studied (e.g., references 1 and 2: Yukihiko Okamura and Fumiyuki Adachi, “Variable-Rate Data Transmission with Blind Rate Detection For Coherent DS-CDMA Mobile Radio”).
Several methods of estimating a transmission rate have been proposed in IS-95 systems as early-type CDMA systems have been proposed (e.g., Japanese Patent Laid-Open Nos. 11-355150, 9-172428, 10-507333, and 11-340840). In these schemes, however, there is no concept that a plurality of TrCH (transport channel) data exist on one channel. Since a W-CDMA system is designed to estimate a transmission rate when a plurality of TrCHs exist on one channel, it is difficult to apply these schemes to this system without any modification.
For estimation of a transmission rate in a W-CDMA system, a method of obtaining a bit length on the receiving side by using path metrics obtained in a Viterbi decoding process (reference 2). This scheme is based on a predetermined data structure (called Fixed Position), and hence is difficult to apply to a new data structure (called Flexible Position). For this reason, a method using CRC is also under study for a new data structure (reference 1).
In such a conventional W-CDMA transmission rate estimation method, however, it takes much time for transmission rate estimation processing for the following reasons, and hence high-speed processing cannot be performed.
First, in the method using the predetermined data structure (Fixed Position), a blank portion called DTX (Discontinuous Transmission) must be prepared in data, and the step of adding or deleting such portion is required.
Second, in the method using CRCs, transmission rate estimation waits until all bits of one block input to a Viterbi decoding section are received, and hence a processing delay becomes large. Since a CRC check is required until transmission rate estimation is completed, the processing time prolongs. In addition, if a CRC check fails, estimation error may occur.